Focus Not Obscured (aa/aaa): revise uses of 'hidden'

[scottaohara]

closes #3446

'hidden' is generally used to refer to content that is not presented to any user (e.g., display none) or 'hidden' from the accessibility tree (e.g., aria-hidden=true).

The current use of 'hidden' in the normative text / understanding doc mostly is meant to mean 'visually hidden/obscured' (though there is an instance of "hidden" in the understanding doc that was referring to the 'completely hidden' definition.

This PR changes instances of 'hidden' that meant 'visually hidden / visually obscured' to use these terms, instead of just 'hidden'.

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[mbgower]

I'm concerned about the normative changes. I agree they're editorial, but my sense is the chance someone is going to wrongfully interpret this is pretty low, and the normative change isn't really warranted.
Is there any reason we cannot just update the Understanding documents

[patrickhlauke]

i tend to agree with @mbgower here ... i don't think there's danger in leaving the normative text as is and just making sure the understanding document explicitly call out that this means visually hidden (from context, i'd say that's pretty clear, as this SC deals with a visual aspect)

[scottaohara]

That’s fair, but @mbgower we talked about this last week on the call and I asked if I should make the normative changes as well while we were on the call, and was told to go ahead. So it’s a bit odd to be told the opposite a week later. I guess there was a misunderstanding

I’ll revert those normative updates later today

[scottaohara]

removed the normative updates, but still reference 'visually hidden' in the notes in each normative doc. should those be removed too? notes aren't normative, so i wouldn't have assumed so? but???